func Polygon(g *geos.Geos, nodes []element.Node) (*geos.Geom, error) {
nodes = unduplicateNodes(nodes)
if len(nodes) < 4 {
return nil, ErrorNoRing
}
coordSeq, err := g.CreateCoordSeq(uint32(len(nodes)), 2)
if err != nil {
return nil, err
}
// coordSeq inherited by LinearRing, no destroy
for i, nd := range nodes {
err := coordSeq.SetXY(g, uint32(i), nd.Long, nd.Lat)
if err != nil {
return nil, err
}
}
ring, err := coordSeq.AsLinearRing(g)
if err != nil {
// coordSeq gets Destroy by GEOS
return nil, err
}
// ring inherited by Polygon, no destroy
geom := g.Polygon(ring, nil)
if geom == nil {
g.Destroy(ring)
return nil, errors.New("unable to create polygon")
}
g.DestroyLater(geom)
return geom, nil
}
func Point(g *geos.Geos, node element.Node) (*geos.Geom, error) {
geom := g.Point(node.Long, node.Lat)
if geom == nil {
return nil, NewGeomError("couldn't create point", 1)
}
g.DestroyLater(geom)
return geom, nil
}
// mergeGeometries
func mergeGeometries(g *geos.Geos, geoms []*geos.Geom, geomType string) []*geos.Geom {
// intersections from multiple sub-polygons
// try to merge them back to a single geometry
if strings.HasSuffix(geomType, "Polygon") {
polygons := flattenPolygons(g, geoms)
polygon := g.UnionPolygons(polygons)
if polygon == nil {
return nil
}
g.DestroyLater(polygon)
return []*geos.Geom{polygon}
} else if strings.HasSuffix(geomType, "LineString") {
linestrings := flattenLineStrings(g, geoms)
linestrings = filterInvalidLineStrings(g, linestrings)
if len(linestrings) == 0 {
return nil
}
union := g.LineMerge(linestrings)
for _, l := range union {
g.DestroyLater(l)
}
return union
} else if geomType == "Point" {
if len(geoms) >= 1 {
for _, p := range geoms {
g.DestroyLater(p)
}
return geoms[0:1]
}
return nil
} else {
panic("unexpected geometry type" + geomType)
}
}
func LineString(g *geos.Geos, nodes []element.Node) (*geos.Geom, error) {
nodes = unduplicateNodes(nodes)
if len(nodes) < 2 {
return nil, ErrorOneNodeWay
}
coordSeq, err := g.CreateCoordSeq(uint32(len(nodes)), 2)
if err != nil {
return nil, err
}
// coordSeq inherited by LineString
for i, nd := range nodes {
coordSeq.SetXY(g, uint32(i), nd.Long, nd.Lat)
}
geom, err := coordSeq.AsLineString(g)
if err != nil {
// coordSeq gets Destroy by GEOS
return nil, err
}
g.DestroyLater(geom)
return geom, nil
}